"When Jack and Annie receive an invitation to spend Christmas Eve in Camelot--a magical place that exists only in myth and fantasy--they know they are in for their biggest adventure yet. What they don't know is that the invitation will send them on a quest to save Camelot. Can they succeed even though Camelot's greatest knights have failed?"--Amazon.com.

While on a mission to prove to Merlin that they can use magic wisely, Jack and Annie travel to seventeenth-century Venice, Italy, to save the city from disaster.

"Jack and Annie search for the fourth secret of greatness for Merlin the Magician in Mexico City at the 1970 World Cup Games. They hope to learn something new from soccer player great, Pele"--

The magic tree house whisks Jack and Annie to Washington D.C. in the 1860s where they meet Abraham Lincoln and collect a feather that will help break a magic spell.

Merlin the magician will not eat or sleep or speak to anyone. The enchantress Morgan asks young Jack and Annie of Frog Creek, Pennsylvania for help. Jack and Annie know they have to search for one of the four secrets of happiness to help Merlin the magician find joy in his life again. And so they head off in the magic tree house for Florence, Italy, in the early 1500s, then to a misty island in the middle of nowhere, then to the continent of Antarctica....

As a thank-you from Merlin and Morgan, Jack and Annie are sent on what should be a vacation at a luxurious resort in Cozumel, Mexico, but is, by mistake, an adventure with ancient Mayans, instead.

Jack and Annie travel in their magic tree house to the land of the mystical selkies to seek a magical sword for Merlin.